It should be possible to get an alert for it by using Advance Triggers in Sentinel. Like for the above-described example, the expression would be as follows -
(LastTradedPrice('NFO:BANKNIFTY21JUN34600CE') * 0.6) >= LastTradedPrice('NFO:BANKNIFTY21JUN34600PE')
* Trade symbols used above are for the June 2021 monthly expiry. For finding the trading symbol for any instrument, use the Technicals option in Kite’s Marketwatch -